Continuous genetic monitoring of transient mesenchymal gene activities in distal tubule and collecting duct epithelial cells during renal fibrosis

Abstract

Epithelial cells (ECs) have been proposed to contribute to myofibroblasts or fibroblasts through epithelial‐mesenchymal transition (EMT) during renal fibrosis. However, since EMT may occur dynamically, transiently, and reversibly during kidney fibrosis, conventional lineage tracing based on Cre‐loxP recombination in renal ECs could hardly capture the transient EMT activity, yielding inconsistent results. Moreover, previous EMT research has primarily focused on renal proximal tubule ECs, with few reports of distal tubules and collecting ducts. Here, we generated dual recombinases‐mediated genetic lineage tracing systems for continuous monitoring of transient mesenchymal gene expression in E‐cadherin+ and EpCAM+ ECs of distal tubules and collecting ducts during renal fibrosis. Activation of key EMT‐inducing transcription factor (EMT‐TF) Zeb1 and mesenchymal markers αSMA, vimentin, and N‐cadherin, were investigated following unilateral ureteral obstruction (UUO). Our data revealed that E‐cadherin+ and EpCAM+ ECs did not transdifferentiate into myofibroblasts, nor transiently expressed these mesenchymal genes during renal fibrosis. In contrast, in vitro a large amount of cultured renal ECs upregulated mesenchymal genes in response to TGF‐β, a major inducer of EMT.

Fibrosis in Chronic Kidney Disease: Pathophysiology and Therapeutic Targets

“…The biological process of epithelial-mesenchymal transition (EMT) constitutes a transdifferentiation of renal tubular epithelial cells (RTEC) in which they lose their characteristic features and undergo a structural change, taking on a more myofibroblastic phenotype [93,129]. With this change, epithelial-specific markers such as E-cadherin and cytokeratin are reduced, while the expressions of mesenchymal markers, such as α-SMA and desmin, are increased, and ECM overproduction ensues [130].…”

“…EMT is a key early phase of fibrosis that is driven largely by TGF-β and is potentially reversible [131,132] (Figure 1). acteristic features and undergo a structural change, taking on a more myofibroblastic phenotype [93,129]. With this change, epithelial-specific markers such as E-cadherin and cytokeratin are reduced, while the expressions of mesenchymal markers, such as α-SMA and desmin, are increased, and ECM overproduction ensues [130].…”